Get ready for summer in October. Just don’t call it Indian Summer…yet.
A big ridge of high pressure in the upper atmosphere has set up shop late this week over the Upper Midwest. What we weather geeks refer to as a “high amplitude jet stream pattern” has set up over the USA. The warmest part or “thermal ridge” will waft through Minnesota over the next 72 hours. Temperatures Thursday PM are in the mid 70s in the metro, upper 70s in western Minnesota and upper 80s in South Dakota today.
The average high for the Twin Cities today is 62 degrees. Temperatures will be running a good 15 to 20 degrees above average in most of Minnesota this weekend.
Even though it’s tempting, it’s too early to call our October warm spell Indian Summer, at least in the metro. Though there have been several hard freezes in northern Minnesota, there has not been a frost in the core of the metro yet. The coolest temp so far at Twin Cities Airport was 38 degrees last Sunday morning.
And yes, there is a definition for Indian Summer.
From the AMS Glossary of Meteorology:
Indian summer–A period, in mid- or late autumn, of abnormally warm weather, generally clear skies, sunny but hazy days, and cool nights.
In New England, at least one killing frost and preferably a substantial period of normally cool weather must precede this warm spell in order for it to be considered a true “Indian summer.” It does not occur every year, and in some years there may be two or three Indian summers. The term is most often heard in the northeastern United States, but its usage extends throughout English- speaking countries. It dates back at least to 1778, but its origin is not certain; the most probable suggestions relate it to the way that the American Indians availed themselves of this extra opportunity to increase their winter stores. The comparable period in Europe is termed the Old Wives’ summer, and, poetically, may be referred to as halcyon days. In England, dependent upon dates of occurrence, such a period may be called St. Martin’s summer, St. Luke’s summer, and formerly All-hallown summer.
The term Indian Summer is largely believed to have originated when European settlers observed native Americans using periods of unusually mild weather late in the season to enhance winter food stores and other supplies.
So enjoy the temps pushing 80 Friday and Saturday, but please…please don’t pull the “Indian Summer” card just yet. You might get some over zealous weather geek correcting you on the spot.